While the Romans were indebted to the Rhodians for their maritime laws, it seems likely that they gained their knowledge of accounts and book-keeping from the Greeks of Crete, who had themselves acquired the elements of this knowledge from the Phœnicians. It is, however, more than questionable whether the Romans improved upon the art. The private arrangements of the Roman merchants and ship-owners respecting the systematic practice of book-keeping were exemplary. Accounts were not actually enforced, as in some modern nations, by positive enactment, but as it was deemed base to charge what was not justly due, so it was held to be nefarious to omit entering what was due to others. The Roman merchants were evidently well acquainted with book-keeping by single entry, as they kept their accounts, _Rationes_,[317] in a book or ledger called _codex_, with headings in columns _accepti_ or _expensi_ (the received and the paid away); they had also a book containing each debtor’s or creditor’s name, and they posted in the ledger, at least once a month, the various items of debit and credit, which it was incumbent on every trader to state fairly and punctually. They had likewise a sort of waste-book (_adversaria_); and it was deemed a suspicious circumstance if entries in this rough book were neglected, and not duly entered on the _codex_[318] in the regular course of business. But though the system of single entry adopted by the Roman merchants and ship-owners much resembles that of modern times, their books were entirely different from those now in use among the traders of Europe and of the United States of America. They were rather rolls[319] of papyrus, each roll or page being divided into columns. The _codex_ or ledger contained the separate accounts, in accordance with the still prevailing practice, headed with the proper name and titles of the respective parties, every transaction being duly transferred or posted into it for permanent observation and record. The ledger was then, as it is now, legal evidence, producible in courts of justice in cases of dispute. It contained in its debit and credit divisions the full account of each transaction. When the _adversaria_, containing the temporary memorandum of the transactions, on which necessary alterations were made before the particulars were transferred to the ledger at the end of each month, if not more frequently, was full, it was thrown aside or destroyed, the ledger being the only record preserved of the transactions which had been completed.